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At least 19 recordsLinked to original sources

[Knee joint prosthesis with the geomedic knee joint (author's transl)].

Thirty-one cases of plastic knee joint operations were reported. Twenty-one patients were treated with the geomedic knee. The advantage of this joint is that only a small amount of bone must be sacraficed. The range of movement is better than that with a complete knee prosthesis with axis.

Aged

Biomechanical evaluation of metacarpophalangeal joint prosthesis designs.

A laboratory biomechanical analysis of metacarpophalangeal joint prosthesis designs was done with fresh cadaver finger rays. The center of rotation, range of motion, tendon excursion, and fingertip force were determined on the specimens before and after implanting Swanson, Niebauer, Steffee II, St. Georg-Buchholz, Schultz, and modified Strickland prostheses. Their biomechanical behavior varied considerably and none duplicated the normal metacarpophalangeal (MP) joint. Each has design characteristics that may be clinically advantageous as well as disadvantageous. Irrespective of the design, the studies done cannot be divorced from the following factors: (1) implant material properties--silicone rubber implants buckled with tendon loading; this deformity created a significant flexor mechanical advantage and an extensor mechanical disadvantage; (2) implant fixation--freely movable implant stems dampened part of the applied load; braided suture provided inadequate immediate fixation; (3) implantation technique--the articulated prostheses can be technically unforgiving; errors in technique resulted in alteration of their biomechanical behavior.

Biomechanical Phenomena

Metacarpophalangeal joint implants. II. Roentgenographic study of the Niebauer--Cutter Metacarpophalangeal Joint Prosthesis.

A roentgenographic study was carried out on 41 Niebauer -- Cutter Metacarpophalangeal Joint Prosthesis from 1 to 36 months postoperatively, a total of 105 examinations. The examinations were performed in the AP-projection and in the lateral projection by tomography in maximum active extension and flexion. The tomographic examinations revealed implant damage of three kinds: cracking within the midsection; fragmentation of the midsection; fracture of the hinge. Cracking within the midsection was found in 8 implants between 6 and 12 months postoperatively and in 1 implant later than 12 months. Later examinations revealed fragmentation of the midsection in 2 implants previously showing cracks. Hinge fracture was observed in 22 implants. Implant damage was found in a total frequency of 26/41. Bone reaction was found on the tomograms in all the operated joints, and could not be evaluated on the AP-projections. A bony spur was found to develop on the metacarpal bone volarly at the site of the osteotomy in 35 joints. In 2 of these the bony spur reached the base of the proximal phalanx, causing anchylosis. Bone resorption was found in 23 joints, constantly dorsally in the metacarpal bone and volarly in the proximal phalanx. The mechanism of the implant damage is discussed with respect to the shearing forces in the joint and the two materials of differing elasticity constituting the implant. The bone reaction is discussed with respect to the intended fixation of the intramedullary stems.

Arthritis, Rheumatoid

Laboratory evaluation of a metal-plastic type of metacarpophalangeal joint prosthesis.

In the normal joint, the conformity of the joint surfaces can provide appreciable dorsal-volar shear stability when a compressive joint force acts. The centers of rotation were within 3 mm of the center of the metacarpal ball. Passive radial-ulna motion at 0 degrees flexion was close to 60 degrees, active motion being half of this; at 90 degrees flexion, there was 37 degrees passive and 23 degrees active motion. Studies of canal shapes and sizes showed that a transverse section deviated from circular by 1-2.5 mm; longitudinal sections were trumpet-shaped but had waves and ripples of about 0.5 mm. This is relevant to cement fixation. A metal-plastic prosthesis was tested in positions and with forces considered applicable to arthritics. It is possible that with plastic components, permanent deformation will progressively occur. The pull-out strength between cement and bone in cadaver bones was about 100 kg; metal stems in cement pulled out at about 50 kg, and plastic stems at 10-20 kg. Slippery stems pulled out at much lower values.

Evaluation Studies as Topic

[On the stress state of bone cement fixing a hip joint prosthesis (author's transl)].

Using a simplified model, tests were made to investigate the shear stress distribution at a hip joint prosthesis. A marked increase of stress at the tip of the prosthesis was found through photoelasticity. This peak stress resulted in a safety factor of 3 against exceeding the shear strength of bone cement. Since the calculation of the stress is based on unfavourable assumptions, the actual factor of safety should show a higher value still.

Bone Cements

[A new intraosseous finger-joint prosthesis].

The faults of interposition-arthroplasty of the finger-joints were shown and intraosseous implantation and intraosseous endoprothesis are presented with initial results. Sources of failure and their treatment are explained and postoperative details and postoperative treatment outlined.

Arthroplasty